FeSeS@C cage-in-cage superlattices for peroxymonosulfate activation: Surface acidity regulates Fe spin state

Two-dimensional cage-in-cage carbon-coated FeSeS superlattices with varying degrees of sulfidation (FeSeS@C) are developed for activating peroxymonosulfate (PMS) to effectively degrade diatrizoic acid (DTZ), and the intrinsic origin that govern the activity of FeSeS@C are deeply elucidated. Experimental and theoretical analyses manifested that proper sulfidation led to increased surface acidity of FeSeS@C. The high surface acidity can optimize the exposure and spin state of Fe sites for FeSeS@C-4, a high spin state of Fe (6.27 μ B ) not only regulating PMS adsorption for enhancing the charge density, but also expediting interfacial charge deliver to trigger the efficient PMS activation. Therefore, among FeSeS@C, FeSeS@C-4 exhibited the best degradation performance for DTZ, with first-order kinetic rate constants (k obs ) of 0.232 min −1 and degradation rate of 100 %. This study demonstrates a novel application of cage-in-cage superlattices in environmental remediation and offers new insights into the mechanism of PMS activation by sulfur modification Fe-based catalysts.